IEEE 802.11n, the latest version of the widely used standard for wireless LANs, promises significant increases in speed by incorporating multiple enhancements at the physical layer. In this paper, the authors demonstrate that, on the contrary, the straightforward deployment of 802.11n in conjunction with TCP over a simple, single access-point network, can dramatically underachieve the promised speeds. Part of the deficiency is due to overheads and can be improved by the technique of packet aggregation present in the standard. However more subtle problems are identified, in particular the downward equalization of throughputs that occurs under physical rate diversity, or the unreasonable portion of resources taken by uplink flows when competing with the more numerous downlink connections.